The dynamics of high autoionizing Rydberg states of Ar.

In this paper we present a theoretical study of the autoionization dynamics of high 2P1/2np′[3/2]1 Rydbergs (with the principal quantum numbers n=100–280) of Ar in weak homogeneous electric fields (F=0.01–1.0 V/cm), which were experimentally interrogated by time-resolved zero-electron kinetic energy (ZEKE) spectroscopy [M. Mühlpfordt and U. Even, J. Chem. Phys. 103, 4427 (1995)], and which exhibit a marked dilution (i.e., ∼2 orders of magnitude lengthening) of the lifetimes relative to those inferred on the basis of the n3 scaling law for the spectral linewidths of the np′ (n=12–24) Rydbergs. The multichannel effective Hamiltonian (Heff) with several doorway state(s) (for excitation and decay) and pure escape states (for decay) was advanced and utilized to treat the dynamics of the mixed Stark manifold of the ZEKE Rydbergs. Heff of dimension 2n-1 is then constructed for a n Rydberg manifold using independent experimental information on the (l dependent) quantum defects δ(l) and the (l, K, J dependent) decay widths, which are of the form Γ0(lKJ)/(n-δ(l))3, with Γ0(lKJ) being the decay widths constants. Here, l, K, and J are the azimuthal, the electronic and the total electronic angular momentum quantum numbers, respectively. Two coupling ranges are distinguished according to the strength of the reduced electric field F(n,p′)=(F/V cm-1)n5/ 3.4×109[δ(p′)(mod1)].Range (A); The onset of the effective coupling of the doorway and escape states, i.e., 0.7≤F(n,p′)≤2. Range (B); The strong mixing domain F(n,p′)≥3. The lifetimes in range (B) can be well represented by a nearly democratic mixing of all the doorway and escape states (lKJ), with the average value <τ(n)>[bar_over_tilde:_approx._equal_to]<τSM(n)>= 2n4h/[J(lJK)Γ0(lJK)]. In range (B) <τ(n)> increases with increasing n and is only weakly F dependent... [ABSTRACT FROM AUTHOR]